Telephone-exchange system



(No Model.)

B. M. BENTLEY. TELEPHONE EXCHANGE SYSTEM.

No. 437,012. Patented Sept. 28. 1890.

'K' A1111 WITNESSES: m INVENTOR:

UNITED STATES PATENT Orrrcn.

ED\VARD M. BENTLEY, OF BOSTON, MASSACIIUSE'I"FS.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 437,012, dated September 23, 1890.

Application filed March 8, 1890. Serial No. 343,112. (No model.)

To [LZZ whom it may concern/.-

Be it known that I, EDW'ARD M. BENTLEY, a citizen of the United States, residing at Doston, in the countyof Suifolk and State of Massachusetts, have invented certain new and useful Improvements in 'lelephone-Exchangc Systems,of which the following is a specification.

IIy invention relates to exchange systems in which part of thecircuits are metallic and part grounded, or in which it is desired to change gradually from grounded to metallic circuits without anymaterial alteration of the ordinary form of switch-board.

It has heretoforebeen proposed in a system wherein metallic circuits are used to have a double connection forboth terminals of each circuit, so that when two subscribers were connected they would be absolutely inclependent of any other connection whatever. This system is obviously cumbersome and cannot be employed where a part of the circuits is grounded. It has, moreover, been suggested that'all the return-lines in a metallic circuit be permanently connected to a ground-plate at the central oflice, which arrangement would leave the present form of switch-board and would also provide for connection with grounded lines; but it is liable to disturbance from earth-circuits, and at the same time whenever a cross occurs with a grounded circuit of high potential the current from the more powerful circuit passes directly to ground through the switch-board, causing damage not only to the line thus crossed, but to all others that may be 0011- nected to the same ground-plate.

My invention consists in bringing both terminals of the metallic circuits into the central station, where one end of each circuit is provided with the ordinary plugsocket or other connecting device for putting it in circuit with other lines, while the other end is connected to a switch which rests normally against a common insulated conductor at the central station, but which may be moved to break the connection. with the said common insulated conductor and establish connection with a grounded conductor. The plugsocket or connecting device is so arranged that whenever it is desired to connect one of the complete metallic circuits with one of the grounded circuits the act of making the con-- nection by the insertion of a plug or other means simultaneously operates the switch to place the opposite terminal of the metallic circuit in connection with the ground. In case, however, that it is desired to put two metallic lines in communication the plug or conuectin g device does not operate the switch, which remains in its normal connection with the insulated conductor.

Referring to the accompanying drawings, Figure 1 is a diagram illustrating my invention. Figs. 9 and 8 represent the connecting device, consisting of a socket and a plug, the two figures respectively showing the two diferent forms of establishing connection. Fig. 4 illustrates a modification.

In the drawings, the lines marked A represent a series of grounded circuits coming into a central station in a well-known manner and terminating each in a connection-socket D, although any other ordinary switch-connection may be used.

The lines marked B represent a series of complete metallic circuits, the two ends of each circuit coming into the central office. Of these two ends one terminates in a socket D, which is connected in the usual manner with an annunciatorE. The other end comes to a switch F, which is located near to the socket D and normally maintains connection with the common insulated conductor G.

It will'be observed that when metallic circuits are to be connected together there will be no change from the ordinary arrangements now employed at the central station. A signal coming in will drop the annunciator E, thereby interrupting the connection with the common insulated conductor G and usually put the listening-operator into communication with the subscriber who desires to be connected with another. Connection is established with the desired line byinserting a plug in the socket D, and a corresponding plug, connected to the first by means of a flexible conductor, is connected to the socket of the other line with which communication is wanted. The same arrangements will be made when communication is desired between any two of the set of grounded lines A. hen, however, it is necessary to connect a line A with a line B, I employ a connection device which not only establishes connection .with the socket D of the metallic line, but in addition operates the switch F to break the connection with the common insulated conductor this by providing a special form of plug, which is somewhat longer than the one employed where connection is only desired between lines of the same class.

The ordinary plug is shown at L, Fig. 2, and the special plug is shown at M, Fig. 3. As indicated in these two figures, the switch F is placed behind the switch-board immediately back of the socket D. The ordinary plug L does not go far enoughinto the socket to press the spring F from its normal con nectionwith common conductor G. Plug M, being somewhat smaller, enters farther into the socket D and throws the spring-switch F from its connection with conductor G into a new connection with conductor K. The same result may be effected in many equivalent ways. For instance, in Fig. 4 I have shown a double.

socket D, which has two openings, one slightly smaller than the other. With this double socket I use but one size of plug, the larger opening being used when it is desired to connect wires of the same class.

By my invention I am enabled to change a system from grounded to complete metallic circuits with practically no alteration in the switch-board, while in cases where a system is composed entirely of metallic circuits I am enabled to use a single connection-plug, and at the same time make connection with trunklines leading to distant exchanges.

What I claim as new, and desire to secure by Letters Patent, is-- 1. The combination, with a series of lines extending from a central station, of returnlines for each, a common insulated conductor at the station, a common ground-conductor at the station, and a switch for each of said return-lines connecting them, respectively, either to the said insulated conductor or to the said grounded conductor.

2. The combination, with a series of grounded lines and a series of metalliclines extending from a central station, of a common insulated conductor at the station to which the said return-lines are normally connected, a common grounded conductor at the station, and a switch for each return-line for disconnecting it from the'said common insulated conductor and connecting it to the said grounded conductor when it is desired to connect one of said metallic lines to one of said grounded lines. A

3. The combination, with aseries of grounded lines and a series of metallic lines extending from a central station, of connecting devices for each line, by which it may bepu-t into circuit with any other, and switches for the return part of the metallic lines normally connecting them to a common insulated conductor, but operated in connection with said connection devices to connect the lines in use with the ground.

4. The combination, with a metalliccircuit having both ends in a central station, of a connection-socket on one end and a switch on the other end vibrating between a groundconnection and-a common conductor resting normally on the latter, and means for making electric connection with said socket-and operating said switch simultaneously.

EDWARD M. BENTLEY.

Witnesses:

N. F. HAYES, A. 0. ORNE. 

